Android那些事

1、使用javah命令获取头文件时，报错“找不到android.graphics.Bitmap”类。

解决方案：在javah命令后面添加 -bootclasspath选项，来指定引导类的路径。这里的引导类为android-sdk/plateforms/android-23/android.jar

2.新浪微博分享不支持arm64Cup架构的手机，，崩溃
使用前检查CPU架构

//获取cpu架构信息线程private class GetCpuInfo implements Runnable {    @Override    public void run() {        try {            InputStream is = null;            InputStreamReader ir = null;            BufferedReader br = null;            try {                File file = new File("/proc/cpuinfo");                if (!file.exists()) {                    return;                }                is = new FileInputStream(file);                ir = new InputStreamReader(is);                br = new BufferedReader(ir);                while (true) {                    String line = "";                    line = br.readLine();                    if (line == null) {                        break;                    }                    if (line.startsWith(KEY_CPU_ARCHITECTRUE)) {                        String[] pair = null;                        pair = line.split(":");                        if (pair.length == 2) {                            if (CPU_TYPE_ARM64.equals(pair[1])) {                                NearApplication.getInstance().getAppConfigDataEngine().setIsArm64Cpu(true);                            }                        }                    }                    Timber.i("line----->" + line);                }            } catch (Exception e) {                e.printStackTrace();            } finally {                if (br != null) {                    br.close();                }                if (ir != null) {                    ir.close();                }                if (is != null) {                    is.close();                }            }        } catch (Exception e) {            e.printStackTrace();        }    }}

3.fragment.startActivityForResult() 可直接在fragment中的onAcitivityResult中接受数据
但是遇到fragment的嵌套时，需要调用fragment.getParentFragment().startActivityForResult() 方法，然后在父fragment中的onActivityResult中接受数据，然后可通过子fragment的引用将数据传递过去。

4.魅族手机开始usb调试后，在mac上不显示连接设备
首先打开终端，输入命令：system_profiler SPUSBDataType，enter之后可以查看连接的各个usb设备的信息，找到供应商ID(Vendor ID)，如MX4的Vendor ID为0x2a45；接着在终端输入：echo “0x2a45” > ~/.android/adb_usb.ini，这个就是把你的设备vid添加到adb连接列表；最后重启dab服务，那么在终端依次输入命令：adb kill-server，dab start-server。

5、命令行签名

jarsigner -verbose -keystore /Users/joye/develop/android/workspace/client/near_android/keystore/near_keystore.jks -signedjar signed.apk /Users/joye/Downloads/tap_unsign.apk release

6.运行时找不到主类
原因：机器中同时运行着两个版本的jdk
解决方案：1、ps aux | grep java 查看所有关于java的进程
2、kill -9 3943 指定线程id杀死

7.打开微信和打开微信特定界面
（1）打开微信
ComponentName cmp = new ComponentName(“com.tencent.mm”, “com.tencent.mm.ui.LauncherUI”);
intent.setAction(Intent.ACTION_MAIN);
intent.addCategory(Intent.CATEGORY_LAUNCHER);
intent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
intent.setComponent(cmp);
（2）其他页面的uri
weixin://dl/scan 扫一扫
weixin://dl/feedback 反馈
weixin://dl/moments 朋友圈
weixin://dl/settings 设置
weixin://dl/notifications 消息通知设置
weixin://dl/chat 聊天设置
weixin://dl/general 通用设置
weixin://dl/officialaccounts 公众号
weixin://dl/games 游戏
weixin://dl/help 帮助
weixin://dl/feedback 反馈
weixin://dl/profile 个人信息
weixin://dl/features 功能插件
Intent intent = new Intent();
intent.setData(Uri.parse(“xxxxxx”));
startActivity(intent);

8.监听home键
方法一：保存每一个activity，在onstop方法中，遍历检查每个activity是否都stop了
方法二：复写activity的onUserLeaveHint方法，但是需要在intent上加flag，Intent.FLAG_ACTIVITY_NO_USER_ACTION
方法三：监听Intent.ACTION_CLOSE_SYSTEM_DIALOGS广播，进一步判断广播类型，示例代码如下

 class InnerRecevier extends BroadcastReceiver {        final String SYSTEM_DIALOG_REASON_KEY = "reason";        final String SYSTEM_DIALOG_REASON_GLOBAL_ACTIONS = "globalactions";       final String SYSTEM_DIALOG_REASON_RECENT_APPS = "recentapps";         final String SYSTEM_DIALOG_REASON_HOME_KEY = "homekey";        @Override         public void onReceive(Context context, Intent intent) {             String action = intent.getAction();             if (action.equals(Intent.ACTION_CLOSE_SYSTEM_DIALOGS)) {                 String reason = intent.getStringExtra(SYSTEM_DIALOG_REASON_KEY);                 if (reason != null) {                     Log.e(TAG, "action:" + action + ",reason:" + reason);                     if (mListener != null) {                         if (reason.equals(SYSTEM_DIALOG_REASON_HOME_KEY)) {                             // home键                             mListener.onHomePressed();                         } else if (reason                                 .equals(SYSTEM_DIALOG_REASON_RECENT_APPS)) {                             // 长按home键                             mListener.onHomeLongPressed();                         }                     }                 }             }         }     }

10、fragment中的onResume 和 onPause方式是activity的方法 通过阅读ViewPager和PageAdapter相关的代码，切换Fragment实际上就是通过设置setUserVisibleHint和setMenuVisibility来实现的，调用这个方法时并不会释放掉Fragment（即不会执行onDestoryView）

@Override    public void setUserVisibleHint(boolean isVisibleToUser) {        super.setUserVisibleHint(isVisibleToUser);        if (isVisibleToUser) {            //相当于Fragment的onResume        } else {            //相当于Fragment的onPause        }    }

11、代码控制字体粗细
在textview中设置画笔的宽度 0 为不加粗（regular） 1为半粗(semibold) 2为粗(bold)

getPaint().setStyle(Paint.Style.FILL_AND_STROKE);getPaint().setStrokeWidth(1);

12、4.0以上的系统会默认开启硬件加速，在绘制虚线的时候会显示成实线，所以需要手动把当前activity或对应的view设置关闭硬件加速

android:hardwareAccelerated="false"view.setLayerType(View.LAYER_TYPE_SOFTWARE, null);

13、监听软键盘的搜索键、确认键

etSearchContent.setOnEditorActionListener(new TextView.OnEditorActionListener() {    @Override    public boolean onEditorAction(TextView v, int actionId, KeyEvent event) {        if(actionId == EditorInfo.IME_ACTION_SEARCH) {            return true;        }        return false;    }});

14、设置动画使用硬件渲染加速
view.setLayerType(View.LAYER_TYPE_HARDWARE, null);
动画结束后要关闭硬件加速 view.setLayerType(View.LAYER_TYPE_NULL, null);

15、colorPrimaryDark 主调色彩加深 （状态栏背景色） colorPrimary 主调色彩（actionbar背景色， 最近任务title背景色和其他边缘效果）
colorAccent 强调色彩 。应用于框架控制（edittext switch）

16、**5.0以上系统在webview设置cookie时，需要添加额外设置
**

if(Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {    cookieManager.setAcceptThirdPartyCookies(webView, true);}

17、获取软件盘高度并监听软件盘的弹出和关闭

View rootView;int screenHeight;ViewTreeObserver.OnGlobalLayoutListener = new ViewTreeOnserver.OnGlobalLayoutListener() {     @Override     public void onGlobalLayout() {     Rect r = new Rect();     rootView.getWindowVisibleDisplayFrame(r);     int keyBoardHeight = screenHeight - (r.bottom - r.top);     if(keyBoardHeight > 0) {          软键盘弹出     } else {         软键盘关闭     }}}

注：r为应用显示的区域，不包含状态栏。(r.left , r.top) (r.right , r.bottom) 分别为这个区域左上角和右下角的坐标。所以当状态栏存在的时候，r.top一直是状态栏的高度。当软键盘弹起时，r.bottom为屏幕顶端（包含状态栏）距软键盘顶部的距离

19、canvas 合成图片 渲染文字

/** * 渲染店铺名称和操作员名称 * * @param canvas       画布 * @param merchantName 店铺名称 * @param textColor    字体颜色 * @param textSize     字体大小 * @param marginTop    距二维码的距离 * @param optName      操作员名称 * @param lineSpace    行间距 */private void drawMerchantNameAndOptName(Canvas canvas, String merchantName, String textColor, int textSize, int marginTop, int bitmapBgWidth, String optName, int lineSpace, int maxWidth) {    TextPaint paint = new TextPaint();    paint.setAntiAlias(true);//抗锯齿    paint.setTypeface(Typeface.DEFAULT_BOLD);    paint.setColor(Color.parseColor(textColor));//字体颜色    paint.setTextAlign(Paint.Align.CENTER);//从中间开始渲染    paint.setTextSize(textSize);//字号    StaticLayout mTextLayout = new StaticLayout(merchantName, paint, maxWidth, Layout.Alignment.ALIGN_NORMAL, 1.0f, 0.0f, false);    canvas.save();    int textPositionX = bitmapBgWidth / 2;//文本渲染位置的X坐标    int merchantNamePositionY = marginTop;//商户名称渲染位置的Y坐标    int operatorNamePositionY = marginTop + textSize * 2 + lineSpace;//操作员渲染位置的Y坐标    if(paint.measureText(merchantName) > maxWidth) {        operatorNamePositionY += textSize + lineSpace;    }    canvas.translate(textPositionX, merchantNamePositionY);    mTextLayout.draw(canvas);    canvas.restore();    paint.setTypeface(Typeface.DEFAULT);    canvas.drawText(optName, textPositionX, operatorNamePositionY, paint);}//背景图片宽高qrcodeBgScaledWidth = bitmapBg.getWidth();qrcodeBgScaledHeight = bitmapBg.getHeight();Timber.i("width----->" + qrcodeBgScaledWidth);Timber.i("height----->" + qrcodeBgScaledHeight);//合成后的图片bitmapResult = Bitmap.createBitmap(qrcodeBgScaledWidth, qrcodeBgScaledHeight, Bitmap.Config.ARGB_8888);Canvas canvas = new Canvas(bitmapResult);canvas.drawBitmap(bitmapBg, 0, 0, null);canvas.drawBitmap(bitmapQrcode, userQrcodeEntity.getImg_conf().getQr_posx() / scaleRatio, userQrcodeEntity.getImg_conf().getQr_posy() / scaleRatio, null);//渲染店铺名和操作员名drawMerchantNameAndOptName(canvas, userQrcodeEntity.getMchnt_name(), userQrcodeEntity.getImg_conf().getFnt_color(), userQrcodeEntity.getImg_conf().getFnt_size() / scaleRatio,        userQrcodeEntity.getImg_conf().getFnt_posy() / scaleRatio, qrcodeBgScaledWidth, userQrcodeEntity.getOpname(), userQrcodeEntity.getImg_conf().getFnt_line_height() / 2, userQrcodeEntity.getFont_width());//保存画布canvas.save(Canvas.ALL_SAVE_FLAG);canvas.restore();

20、使用Service时，解绑连接的时候只能调用unbindService(ServiceConnection);一次，第二此调用会报错：
java.lang.IllegalArgumentException: Service not registered

21、在布局右侧的EditText，包含默认的hint，如何让光标居右
设置属性android:textCursorDrawable = “@null”

22、向相册中插入图片

public static boolean saveImage2Gallery(Context context, String filePath, String fileName) throws IOException {    if (context == null || fileName == null || filePath == null) {        Log.e(TAG, "saveImage2Gallery: context: " + context + ",filePath: " + filePath + ",fileName: " + fileName);        return false;    }    File file = new File(filePath, fileName);    if (!file.exists()) {        throw new FileNotFoundException();    }    if (isPicMedia(fileName)) {        ContentResolver contentResolver = context.getContentResolver();        //向多媒体数据库中插入一条记录        ContentValues values = new ContentValues(3);        values.put(MediaStore.Images.Media.TITLE, "");        values.put(MediaStore.Images.Media.DESCRIPTION, "");        values.put(MediaStore.Images.Media.MIME_TYPE, "image/jpeg");        Uri url = contentResolver.insert(MediaStore.Images.Media.EXTERNAL_CONTENT_URI, values);        //查询新创建记录的id        if (url != null) {            long id = ContentUris.parseId(url);            OutputStream outputStream = null;            FileInputStream fileInputStream = null;            try {                outputStream = contentResolver.openOutputStream(url);                //向uri中写图片数据                fileInputStream = new FileInputStream(new File(filePath, fileName));                byte[] buffer = new byte[1024 * 5];                int len;                while ((len = fileInputStream.read(buffer)) != -1) {                    if (outputStream != null) {                        outputStream.write(buffer, 0, len);                    }                }            } catch (IOException e) {                e.printStackTrace();                throw new IOException();            } finally {                try {                    if (outputStream != null) {                        outputStream.close();                    }                    if (fileInputStream != null) {                        fileInputStream.close();                    }                } catch (IOException e) {                    e.printStackTrace();                }            }            //生成缩略图            Bitmap miniThumb = MediaStore.Images.Thumbnails.getThumbnail(contentResolver, id,                    MediaStore.Images.Thumbnails.MINI_KIND, null);            //将缩略图插入到数据库            Bitmap microThumb = StoreThumbnail(contentResolver, miniThumb, id, 50F, 50F,                    MediaStore.Images.Thumbnails.MICRO_KIND);            FileUtil.deleteFile(new File(filePath, fileName));            return true;        }        return false;    } else {        Log.e(TAG, "saveImage2Gallery: file type error. fileName : " + fileName);        return false;    }}

23、DatePicker不能重复设置最大日期和最小日期

if (mTempDate.get(Calendar.YEAR) == mMinDate.get(Calendar.YEAR)&& mTempDate.get(Calendar.DAY_OF_YEAR) != mMinDate.get(Calendar.DAY_OF_YEAR)) {    return;} ———bug here

24、在dimens文件设置浮点数
In dimen.xml

<item name="float" type="dimen" format="float">9.52</item>

Referencing from java

TypedValue typedValue = new TypedValue(); getResources().getValue(R.dimen.my_float_value, typedValue, true); float myFloatValue = typedValue.getFloat();

25、状态栏高度

public static int getStatusBarHeight(Context context) {        Class<?> c = null;        Object obj = null;        java.lang.reflect.Field field = null;        int x = 0;        int statusBarHeight = 0;        try {            c = Class.forName("com.android.internal.R$dimen");            obj = c.newInstance();            field = c.getField("status_bar_height");            x = Integer.parseInt(field.get(obj).toString());            statusBarHeight context.getResources().getDimensionPixelSize(x);            return statusBarHeight;        } catch (Exception e) {            e.printStackTrace();        }        return statusBarHeight;    }

public static int getStatusHeight(Activity activity) {        int stausHeight;        Rect frame = new Rect();        activity.getWindow().getDecorView().getWindowVisibleDisplayFrame(frame);        stausHeight = frame.top;        return stausHeight;    }

public static int getStatusBarHeight(Context context) {        int result = 0;        int resourceId = context.getResources().getIdentifier("status_bar_height", "dimen", "android");        if (resourceId > 0) {            result = context.getResources().getDimensionPixelSize(resourceId);        }        return result;    }

26、启用webview的缓存

settings.setAppCacheEnabled(true);String cachePath = mContext.getCacheDir().getAbsolutePath();if(Build.VERSION.SDK_INT <= 20) {    //4.4以下需手动设置database路径,方使domstorage生效    cachePath += "/database";    settings.setDatabasePath(cachePath);}Log.d(TAG, "setWebViewSetting: cachePath--->"+cachePath);settings.setAppCachePath(cachePath);settings.setAllowFileAccess(true);

27、adb shell dump sys activity 查看Activity栈

28、减法、除法不精确的问题
使用BitDecimal进行加减乘除

29、
textview.getPaint().setFlags(Paint.STRIKE_THRU_TEXT_FLAG |Paint.ANTI_ALIAS_FLAG);加上这个属性，字体更清晰一些